The investigation dates back to November 2011, when a federal agent working undercover identified a suspect with the screen name "Kidluver," who was sharing child porn files through peer-to-peer software.

Federal agents traced the screen name and online activity to Corbitt's home in Washougal, the U.S. Attorney's Office said.

They then served a search warrant there on Feb. 1, and that's when they learned he was employed as a pediatric intensive care nurse at Doernbecher Children's Hospital.

A laptop was seized by police when they searched his home. Court documents said Corbitt admitted in an interview with police that he used the screen name "Kidluver" and told agents he has been looking at child pornography for at least 10 years.

U.S. Attorney Jenny Durkan said federal agents are working closely with the hospital "to identify the full scope of the criminal conduct in this case, and to identify any victims."

Corbitt, who began working in Doenbecher's pediatric intensive care unit in July 2002, was placed on unpaid administrative leave Feb. 1. He then resigned Feb. 10.

The hospital is making contact with patients who may have interacted with Corbitt. Patients or families with concerns are asked to call OHSU Patient Relations at 1-855-650-3900.

Corbitt is expected to make a federal court appearance in Tacoma, WA, on Friday afternoon.

Portland police seized multiple guns after serving a search warrant at a home in Gresham and Clackamas County. Around 5 a.m. on Wednesday, police along with East Metro County SWAT conducted a search warrant at a home in the 1000 block of Northeast 173rd Avenue and arrested Ervan Herring, 43. The Clackamas County SWAT also arrested Michael Herring, 43, during a search warrant at a home in the 16300 block of Southeast 135th Avenue.

Portland police seized multiple guns after serving a search warrant at a home in Gresham and Clackamas County. Around 5 a.m. on Wednesday, police along with East Metro County SWAT conducted a search warrant at a home in the 1000 block of Northeast 173rd Avenue and arrested Ervan Herring, 43. The Clackamas County SWAT also arrested Michael Herring, 43, during a search warrant at a home in the 16300 block of Southeast 135th Avenue.